[boost] access violation using boost::thread_specific_ptr

From: Oscar Ciurana (oscar_at_[hidden])
Date: 2003-08-08 02:17:21

Hi,

I'm working with boost::thread_specific_ptr in a Win32 environment and
sometimes I get an access violation
when my program exits. To reproduce the error I write the following
sample program:

...
#include <boost/thread/thread.hpp>
#include <boost/thread/tss.hpp>
#include <iostream>

class Data
{
public:
 ~Data()
 {
  std::cout << reinterpret_cast<int>(this) << std::endl ;
 }
} ;

typedef boost::thread_specific_ptr<Data> ThrData ;

void main()
{
 ThrData data ;
 data.reset( new Data ) ;
 data.reset() ;
}
...

You can see how the Data destructor is called twice, one in the
data.reset() execution and the second when the program
exits.

I was examining the boost source code and I think the problem is in the
file libs\thread\src\tss.cpp
...
bool tss::set(void* value)
{
    if (value && m_cleanup)
    {
        cleanup_handlers* handlers = get_handlers();
        assert(handlers);
        if (!handlers)
            return false;
        cleanup_info info(m_cleanup, value);
        (*handlers)[m_key] = info;
    }
    return !!TlsSetValue(m_key, value);
}
...
In this function when value is a NULL pointer the cleanup_info data is
not actualized. So when the thread ends
it will delete the data that was deleted previously with the
boost::thread_specific_ptr::reset() method.

I think the solution is
...
bool tss::set(void* value)
{
    if (m_cleanup)
    {
....
This way a NULL pointer actualizes the cleanup_info data, but I don't
know if there is any lateral effect when removing
value from the 'if' sentence.

Regards,
Oscar.